We present a rare case of a 77-year-old Japanese man with malignant lymphoma associated with production of beta-subunit of human chorionic gonadotropin in the cytoplasms of lymphoma cells in the lymph nodes. By immunoperoxidase staining, numerous tumor cells were reacted with beta-subunit of human chorionic gonadotropin. To the best of our knowledge, production of beta-subunit of human chorionic gonadotropin in the cytoplasm of lymphoma cells has not been reported. This patient evidences that beta-subunit of human chorionic gonadotropin may be produced by tumor cells, therefore, beta-subunit of human chorionic gonadotropin may be used as a tumor maker in some malignant lymphoma patients. Acta medica Nagasakiensia. 1991, 36(1-4), p.52-54